Re: [PATCH] [RFC] c/r: Add UTS support

["Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org>]

Quoting Dan Smith (danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org):
> SH> Well it forces restart to go through the established userspace
> SH> API's when creating resources (in this case, tasks and namespaces)
> SH> which means any existing security guarantees are leveraged.
> 
> That's a very valid point.  However, it still seems unbalanced to make
> checkpoint a completely in-kernel process and restart an odd mix of
> the two with potentially more confusing semantics and requirements.

core_dump vs gdb? :)

> SH> If we go with your patch, we suddenly have to worry about whether
> SH> restart is a way to get around the CAP_SYS_ADMIN requirements for
> SH> cloning a new namespace.  Just as an example.
> 
> Why?  The call to copy_namespaces() will do the CAP_SYS_ADMIN check,

Had to check, but yes you're right.

> right?  Maybe your point is that in the restart implementation of
> other namespace types we could potentially slide in a call to
> something else that has already assumed the check has been made?  I
> think that doing the obligatory copy_namespaces() during the restart
> helps catch that case early and explicitly, no?

Actually we can go a step further and say we expect user-space to
set the hostname, which otherwise (admittedly in a container) the
user, with your patch, can now do unprivileged, right?

In particular, once it comes to setting up network devices for a
container at restart, I think we'll find userspace a far easier
place to work.

-serge